FIG. 1 illustrates a known industrial automation input output module 100 comprising a housing 102 constructed from inner and outer housing members 102a,102b that are inter-fitted with each other to define an enclosed interior space 104 in which one or more electronic circuit boards 106 is/are located. The inner and outer housing members 102a,102b are each preferably defined as one-piece molded polymeric constructions utilizing any of a wide variety of polymeric materials in an injection molding process. One suitable material is glass-filled polyester, although it is not intended that the development be limited to such material or any other material. One or more connectors 108 are operably connected to the circuit board 106 and project through a top face 110 of the outer housing member 102b so as to be adapted for mating with corresponding cable connectors from external input output devices or the like. The circuit boards 106 and connectors 108 are adapted for any desired electrical application such as input and output to/from an industrial process. A module 100 typically comprises a plurality of visual indicators such as light emitting diodes operably connected to a circuit board 106 and that provide visual output signals concerning the state of the circuitry 106 in the module 100 and/or flow of data or power or other signals. A light pipe includes lenses 114 that are aligned with and/or project through respective openings 116 in the top face 110 of the outer housing member 102b or other location of the housing 102 to communicate light from the LED's outside of the module 100.
The connectors 108, light pipe lenses 114 and any other openings in the outer housing member 102b are sealed against ingress of water, dirt or other contaminants to the interior space 104 using a potting compound PT that is applied into the outer housing member 102b after the various components such as the connectors and light pipe are installed. Often, multiple layers of potting compound PT are used and installed/cured in stages as components are correspondingly added in stages.
Potting compound PT is also used to seal the connection between the inner and outer housing members 102a,102b. In the illustrated example of FIG. 1, it can be seen that the inner housing member 102a is adapted for nesting within the outer housing member 102b and comprises a plurality of tabs 102T that are received in corresponding recesses 102R such as notches, or apertures defined by the outer housing member 102b so that the housing members 102a,102b are mechanically interlocked with a close snap-fit. Furthermore, the inner housing member 102a comprises a continuous peripheral wall 102W projecting outwardly therefrom that is received within a corresponding continuously extending peripheral groove 102G defined by the outer housing member 102b. The joint at the junction of the wall 102W and groove 102G is sealed with the potting compound PT.
Despite widespread commercial success, the module 100 of FIG. 1 has various drawbacks relating to the use of potting compound PT to provide the requisite ingress protection. Potted products cannot be disassembled and repaired. A batch of defective modules 100 must be discarded even if only a single component of each module is defective. Assembled modules 100 that are potted cannot be disassembled and reconfigured. The potting compound PT must be cured by passage of time and/or application of heat, neither of which is desirable in a manufacturing system. The potting compound PT is dense and adds significant weight to the product. The presence of potting compound PT also prevents recycling of the module 100.
With these and other concerns in mind, an industrial automation input output module with elastomeric sealing, and a method of constructing same, have been developed and are disclosed herein according to the present invention.